The objective of this study is to explain decreases in dental caries prevalence in non-fluoridated areas and to determine reasons for any increases in dental fluorosis. The study will include the collection of comprehensive data on exposure to fluoride from all sources by children and adolescents. Two communities located in a geographic region classified as a "high fluoridation" area -- one with a central water supply which is "fluoride deficient" (less than 0.3 ppm fluoride) and one which has been optimally fluoridated continuously since 1980 or earlier-- were selected for study. Within each community approximately 400 (ages 12 and 13 years) life-long residents were asked to participate in the study. These subjects were examined for dental caries and enamel fluorosis. Samples of plaque, saliva, blood and urine were collected from the subjects and evaluated for their fluoride concentrations. A dietary data and a detailed information on residence and fluoride-use history were obtained from each subject, as well as sociodemographic, and behavioral information. In addition, water samples were collected from community sites and school buildings for analysis; and frequently consumed foods, as listed in the dietary histories, will be purchased locally and analyzed for fluoride content. Fluoride distribution in body fluids and tissues will be correlated with each other and with reported intake, clinical findings of dental enamel fluorosis, and dental caries experience. These relationships will be evaluated between the communities and between groups of individuals with different fluorosis manifestations. This year the following progress was made. The most frequently consumed foods, specific product names and methods of food preparation were determined by follow-back calls to families. The 75 products from each community were purchased, prepared and analyzed in the laboratory for fluoride content. Specific fast food items and prepared products were processed together and one determination made by brand or item name. All clinical examination data, biological specimens fluoride content, questionnaire items and food fluoride were collected, edited and data files prepared for delivery to NIDR. Preliminary analysis of clinical and biological data was initiated.